If you have a real 68 balancer the timing marks on it will be on the passenger side. You will need to remark it, or just time it by ear.
I think the 66-68?? LA 273s and 318s had a bolt on timing tab that you can also use to solve that problem. I had one on mine for awhile. They are hard to find, but usually only $20-30.
You could buy a new one marked properly, but you need to make sure you get one matched to your crankshaft. I think the cast crankshaft started in 72 or 73. With a 60 year old engine, who knows what is in it…